Poppet valve and guide assembly



Dec. 3; 1946. w. D. APPEL POPPET VALVE AND GUIDE ASSEMBLY Filed Sept.16, 1944 1 ATTORNEE} Patented Dec. 3, 1946 UNITED 1 STATES PATENTo1=1=1cs I POPPET vanvn li Nii iimn ASSEMBLY I Walter B. Appel, OrchardLake,

to General Motors Corporation, Detroit,

Mich., assignor Mich a corporation of Delaware Application September 16,1944, Serial No. 554,355

3 Claims. (Cl. 123-188) The use of high octane leaded fuel in internalcombustion engines has created a problem which stems to become so stuckin the valve guides that the springs cannot overcome the resistance andclose the valves. Thereupon the combustion chamber gases pass around thevalve heads, burn the heads and stems and soon the valves must bereplaced. In the case of lower octane fuels similar but lessserioussticking occurs and in such cases the difficulty has been to some extentlessened'by the use of counterbored guides or reduced valve stemdiameters within the ends of the guides.

The present invention has taken cognizance of these prior expedientadopted to overcome the effects of carbon deposits from relatively lowoctane fuels but it has been found that a mere unscientiflcallycounterbored guide or a two diameter stem is not enough to solve thepresent problem.

Very briefly stated, the problem hasbeen solved by resort to a. twodimension valve stem movable in a'valve guide having a bore of uniformdiameter, the partsbeing so dimensioned relative to the position of thevalve head and its seat and the stroke of the cam that the shoulderbetween the parts of the stem shall always be within the guide and shallapproach but not reach the end of the guide as the valve opens. The bestresults also require that the radial dimension of the annular spacebetween the reduced dimension part of the stem and the wall of the guideshall be such as to permit the collection of a moderate coating of leaddeposit on the stem but that it shall not be so large as to permit aturbulence of gas within the space and consequently the carrying of muchof the lead deposit into this chamber. The axial dimension should not beextended unduly else the stem will not be properly guided and the valvewill not seatas it should. 7

The structure which is believed to bethe best to carry out the inventiveidea is shown on the accompanying drawing, in which: A

Fig. 1 is a view in elevation of a conventional valve assembly.

Figs. 2 and 3 are similar views of my new assembly with the valve in twodifferent positions.

While with certain valve dimensions good result may be had from the useof a counterbored guide this invention makes use of a guide with auniform bore through which slides a two dimension stem. Among thereasons for selecting the second of these expedients are the following.The length of annular chamber is constant when one counterbores theguide whereas with the two dimension stem the guiding portion of theguide increases in length as the valve opens. Also there is no provisionforremoving ..the deposit on the inner wall of the counterbored guide.On the contrary, the shoulder between the two parts of the two dimensionstem scrapes the deposit from the walls of the guide due to the positiveaction another and very important reason for selecting the second of thetwo expedients. The hot gases from around the valve head build updeposits along the stem. Near the head the more intense heat burns theseto a kind of film but a, little way down the stem, where the heat issomewhat less,

there is found a bulbous deposit of some appreciable size. This bulbousdeposit, if it gets within the counterbore of a guide necessitates another-. wise needlessly large counterbore to prevent sticking. With areduced dimensioned stem having less heat conducting metal thecritically hot region is nearer the valve head and hence the bulbousregion at the lower end of the critically hot region is further from theend of the guide.

Since it is nearer the head it is well above the end of the guide anddoes not cause sticking because of contact with the guide. A depositdoes collect on the end of the guide, and just within the end. Thereforethe shoulder which is within the guide should be so located that,invalve position, it will not contact this deposit. As a mat- 'ter offact the deposit at the guide opening is of use in that it partly closesthe annular space within the guide and around the stem thus sealing offthis space to such an extent as to prevent the lead deposits beingcarried into the space by the turbulent gases outside. There aretherefore many reasons for reducing the stem diameter rather thancounterboring the guide. The experiments have shown that very goodresults are obtained with a valve having a 13-32 inch stem reduced to11-32 inch from the valve head for a distance of about 1% in. theshoulder being always in the guide and the movement being such that,when the valve. is opened by the cam, the shoulder shall be about y in.from the end of the guide. This will avoid the danger of the largediameter part sticking to the deposit just within the guide opening. I1,too; the radial of the cam. There is dimension of the annular'space isbetween 752 and in., the space has been found to be suflicient toaccommodate the slight collection. of deposit on the stem which willoccur in spite of the nearly closed annular space. As explained above,any deposit on the inner wall of the guide except that adjacent theopening beyond the limit of outward movement of the shoulder on the stemis scraped off by the shoulder.

It is believed that the invention will be understood from thedescription above. The drawing serves to illustrate it. On the drawing,the old type of valve assembly is shown by Fig. 1. Here the valve guide5 has a uniform bore and the valve stem.'l is also of uniform diameter.The

valve head 9 is showniseated. As explained above, the tendency tocollect a deposit on the stem adjacent the end of the guide is indicatedby a bulbous formation marked I I (exaggerated). It will be readily seenthat the deposit may cause the valve to stick at the end of the guide sothat the releasing spring may be unable to break it away. Fig. 2 showsthe same valve guide 5 but my improved valve with its stem 1' reduced indiameter as at [3 from the head to a point marked a which is well withinthe guide when the valve is seated. Also the reduced diameter of thevalve stem 1' has caused the bulb II to form further from the end of theguide than before, so that it cannot cause sticking. The

shoulder at a moves from the position shown by deposit and carry anundue seen that this deposit l5 partially Fig. 2 toward the open end ofthe guide and scrapes on. any deposit which may form on the wall of theguide. However, a shown by Fig. 3, when the valve reaches its openposition the shoulder is still a little Way from the end of the guideand does not engage and stick to the I5 which forms at the end of andextends little way into the guide. It will also be closes the annularchamber at the end of the guide so that the turbulence outside may notextend thereinto quantity of carbon or lead products into the chamber.

I claim:

v 1. A valve and guide assembly, said valve havingan integral stem withparts of two different diameters forming a shoulder therebetween, theparts being so, proportioned that the shoulder is always within theguide and that the shoulder approaches but does not reach the end of theguideon the valve opening movement.

2. The invention defined by claim 1, the difference in diameter beingsuch as to permit only a slight deposit within the space around the stemwithin theguide.

3. The invention defined by claim 1, the opening movement of the valvecarrying the shoulder to a limit at. about one-eighth of an inch fromthe end of the guide.

just a WALTER, D. APPEL.

